Larger helicopters, in general, have several features in common in a basic configuration or layout. For instance, a typical helicopter will have a cabin section rearward of the pilot's cockpit or flight deck and which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment, which is located typically above and to the rear of the pilot's cockpit or flight deck and above the cabin section. The engine compartment typically houses two primary components, at least one engine and a rotor transmission at least partially contained within a transmission housing.
Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section unless proper sealing mechanisms are in place. The inflow of these leaking fluids can spoil, stain, or damage the cabin's interior materials, such as, seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of a helicopter.
During routine inspection and maintenance it is necessary to have both ready visual and physical access to portions of the engine or at least the rotor transmission. Such access is required to check critical fluid levels; to replace worn, damaged or depleted parts or filters; or to adjust mechanical systems. Typically, various access panels in or around the engine or transmission compartments provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, a forged or fixed airframe structure forms an access opening that is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin's ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage into the cabin.
The access opening below the engine compartment in the helicopters, such as the “M” model BLACKHAWK® helicopter, made for the United States by Sikorsky Aircraft Company of Stratford, Conn., is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter's forged structure. The skirt is thin and many times more flexible relative to the helicopter's forged structure.
Prior cover designs included a covering plate that is attached directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as, the protruding rivet heads from the rivets that secure the skirt to the forged helicopter structure. When the seal engages both the skirt and the rivet heads, it may be displaced or deformed enough to create gaps between the seal and the skirt. Leakage of fluids past the seal may then occur. Accordingly, the hollow seal traversing these aberrations, though sandwiched between the skirt and the covering plate, is generally unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt during operation of the helicopter could, in addition or alternatively to gapping described above, also cause the seal to gap thereby allowing fluid leakage. Drip pan structures disclosed in U.S. Pat. Nos. 6,112,856; 6,216,823; 6,446,907; and Design Pat. No. D444,443, which are fully incorporated herein by this express reference, provide improvements and solutions to the aforementioned difficulties.
The “M” model is being produced by Sikorsky and is in service with the U.S. military, for example, in Afghanistan. In the “M” model, and in other aircraft with what are or will be similarly-shaped skirts, the access opening has at least one corner of the skirt pulled outwardly to allow direct and straight-through access to the filter, alleviating the need to tilt or otherwise reorient a filter for removal and/or installation in prior model BLACKHAWK® helicopters. However, the aforementioned structures are not readily adaptable for use with the “M” Model BLACKHAWK® helicopter due to a change in configuration of the skirt. In this regard, an improved drip pan apparatus for such a skirt configuration, such as that disclosed in U.S. Publication No. 2009/0159739, which is incorporated herein in its entirety, addresses the problems created by the “M” model skirt configuration.
In addition to shielding the cabin from fluid, the geometry of the pan structures cannot protrude significantly into the interior of the cabin section. Any protrusion from the ceiling that further reduces the available head room of the cabin section is undesirable and may be prohibited by regulation. For example, regulations may prohibit protrusions which decrease the available “head room” for a person of a specific height or taller. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable.
However, in addition the aforementioned problems and limitations, other problems and limitations have been identified with the “M” model. In this regard and by way of example, FIG. 1 shows a configuration of a typical BLACKHAWK® helicopter 10, for example, a “M” Model BLACKHAWK® helicopter. In the configuration shown, the helicopter 10 has a cabin 12 (dashed outline) in which passengers, equipment, and cargo may ride during flight. Located just above the cabin 12 is at least one engine 14 which powers to a rotor transmission 16. The rotor transmission 16 is operatively connected to a shaft 18 which imparts rotary motion to the main rotor 20. The rotor transmission 16 is also operatively connected via a drive shaft (not shown) to a tail rotor 22.
The rotor transmission 16 requires frequent inspection and maintenance to ensure its proper operation. To facilitate easy and ready access to the rotor transmission 16, one or more rotor transmission access openings may be provided on both the exterior and interior of the helicopter. For example, a transmission access opening 205 may be located within the cabin 12 to provide the requisite access to the rotor transmission 16 that is situated directly above the cabin 12. The access opening 205 generally has some type of removable cover, to separate the transmission 16 from the cabin area 12.
As shown in FIG. 2A, to accommodate attachment of such a removable cover, a flexible skirt 207 may be secured to an airframe member 206 around the periphery of opening 205 by rivets 28. Skirt 207 may be many times more flexible than the access opening 205 as is defined by the airframe member 206, to which it is attached. To prevent leakage of fluid into the cabin 12, a pan structure, for example, a drip pan apparatus 200 shown in FIGS. 2A, 2B, 3A, and 3B may be used to cover and seal the access opening 205.
The cabin 12 is more fully illustrated in FIG. 3A. The helicopter 10 may be equipped to transport personnel or equipment generally or may be equipped for a specific mission or to perform a specific function. By way of example, the interior of the cabin 12 may be outfitted with the equipment necessary to insert and/or extract soldiers from the battlefield. In this regard, a Fast-Rope Insertion and Extraction System (FRIES) 30 may be installed to the ceiling of the cabin 12 below the transmission 16.
The FRIES 30 generally includes a main tube or bar 32 that may be secured to the airframe member 206 (shown in FIG. 2A) with barrel nuts (not shown) or the like on both sides of the access opening 205. The bar 32 generally spans the access opening 205 and is positioned directly below the drip pan apparatus 200. The FRIES 30 may include one or more extendable/retractable or telescoping locking mount bars 34 that slidably engaged the bar 32. The telescoping bars 34 may be selectively extendable to project from the cabin 12. In operation, once the bar 34 is extended, one or more rappelling ropes or a cable (not shown) may dangle from one of the bars 34. In this extended configuration, personnel may rappel from the helicopter 10 or be extracted from a lower surface while the helicopter 10 remains aloft.
As shown in FIG. 3A, attachment of the FRIES 30 to the ceiling of the cabin 12 leaves little, if any, clearance between the drip pan apparatus 200 and the bars 32, 34. As is described in more detail below, the lack of clearance between the bars 32, 34 and the drip pan apparatus 200 creates problems with the inspection and maintenance of the transmission 16 via access opening 205 and restricts the configuration, including the dimensions, of the drip pan apparatus 200. By way of example, the FRIES 30 may be spaced from the drip pan apparatus 200 by at most about 2 inches, and by way of additional example may be spaced from the drip pan apparatus 200 from about one-half inch to about 2 inches. It will be appreciated that other bar configurations may be secured to the airframe 206, span the access opening 205, and may be used to support a winch or other device for lowering and/or lifting personnel, weapons, or other equipment to or from the cabin from below the helicopter 10. Furthermore, other equipment, for example, troop seat bars (not shown), may be supported by other bar configurations secured to the ceiling of the helicopter in the same or similar position as the FRIES 30 and impede access to the transmission 16 and, in some instances, block access to the tabs 202 (described below) along one or more sides of the apparatus 200.
By way of additional example and with reference FIG. 3B, the helicopter 10 may be equipped as a MedEvac. In this regard, a medevac bar 40 rather than the FRIES 30, described above, may be secured to the ceiling of the cabin 12. Typically, similar to the bars 32, 34, the medevac bar 40 is attached to the airframe member 206 on each side of the access opening 205 such that the bar 40 spans across the access opening 205. As such, the medevac bar 40 is directly below the drip pan apparatus 200. However, unlike the FRIES bar 32, 34, the medevac bar 40 generally defines a top rotation point of a rotatable partition 42 that partially divides the cabin 12 and that supports one or more litters or stretchers 44. The partition 42 may be selectively positionable about an axis 46. Stretchers may be loaded onto the partition 42 and the partition 42 may then be rotated 90 degrees prior to helicopter liftoff.
When the helicopter 10 is so equipped, the medevac bar 40 is spaced from the drip pan apparatus 200. The clearance between the drip pan apparatus 200 at any particular location and the medevac bar 40 may be less than that of the FRIES bars 32, 34. For example, the clearance between the medevac bar 40 and the drip pan apparatus 200 may be on the order of a few thousandths of an inch and may be roughly equivalent to the thickness of a sheet of paper (e.g., 0.002 to 0.006 inches).
In each of these exemplarily equipped helicopters, the mission specific equipment is positioned immediately or directly below the drip pan structure. The position of the equipment and the necessity that it be securely fastened to the frame member 206 complicates access through the access opening 205. As a result, inspection and maintenance of the transmission 16 from within the cabin 12, which may only be accessible via the access opening 205, is made troublesome or nearly impossible by the mission specific equipment. Generally, the mission specific equipment may span the access opening 205 or otherwise partially block or interfere with access to the transmission 16 through the access opening 205, as is exemplified by the Medevac or FRIES bar, above. In spite of this interference or blockage, the configuration of the drip pan structure must allow for attachment of mission critical equipment on the one hand, but allow for inspection of the transmission 16 and, when necessary, removal of the pan structure or at least a portion thereof without removal of the mission critical equipment on the other hand.
For instance, the FRIES 30 (FIG. 3A) or the medevac bar 40 (FIG. 3B) interferes with the inspection and maintenance of the transmission 16 via the access opening 205. However, removal of either one to gain full access through the access opening 205 may require initial removal of other equipment, for example, the associated rotatable partition 42 in the case of the medevac bar 40. Similarly, removal of the FRIES 30 that spans the access opening 205 is not only difficult or impossible without damaging that or other equipment or helicopter 10, but it is also time consuming. Thus, full access through the access opening 205, while desirable, is often not economically nor logistically feasible once the helicopter 10 is outfitted for a specific mission or purpose. Although specific mission equipment (e.g., the FRIES 30 and medevac bar 40) are described above, it will be appreciated that other similar systems may be installed to the ceiling in the cabin 12 to provide similar or alternative functions for a specific mission or operation.
In addition to the space constraints imposed by mission specific equipment or possibly due to the space constraints, applicant recognized another issue with the BLACKHAWK® “M” model helicopter. In particular, the “M” model fails to provide sufficient clearance between the transmission and the prior drip pans and/or within the cabin between the cabin floor and prior pans. That is, one or both of these dimensions may be insufficient. As is described in more detail below in conjunction with FIGS. 4 and 5, there is a wire bundle that passes between the transmission and prior pan. It was recognized that the wire bundle for the “M” model is larger than previous models, and that the distance between the transmission and prior pans would not adequately accommodate the relative increase in size. A solution to which is exacerbated by the spacial constraints set forth above. Accordingly, simply moving the pan structure away from the transmission may not be a solution and may cause additional problems.
Accordingly, it is one objective to provide an improved leak-proof drip pan structure for use in BLACKHAWK® helicopters.
Another objective is to provide an improved drip pan structure that will allow inspection of an engine or transmission compartment from a cabin section of a helicopter without first removing mission specific equipment from the cabin section thereof.
Another objective is to provide an improved drip pan structure that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a BLACKHAWK® “M” model helicopter and similar airframes.
Another objective is to provide an improved drip pan structure which permits quick visual and physical access to the engine or transmission compartment of a BLACKHAWK® “M” model helicopter and similar helicopters without requiring modification to the existing aircraft structure.
Still another object of this invention is to provide a drip pan structure that can be attached to the existing structure of a BLACKHAWK® “M” model helicopter while both improving the headroom available in the cabin and providing clearance to other existing components, including a wire bundle, proximate the transmission.